Sustainable Energy Conversion Research Articles

Free standing MoSe2 growth on porous Graphite-Like membranes for water splitting

Clean hydrogen made from water-splitting through the hydrogen evolution reaction (HER) is important for sustainability and reducing pollution. Exploration of high-efficiency Pt-free electrochemical catalysts for HER is considered a great challenge for the development of sustainable and carbon dioxide-free energy conversion systems.For that, electrocatalytic electrodes made of self-standing binder-free materials have been extensively employed in hydrogen production. Herein, the gelatin and graphene oxide cryogels were cryogeleted and then carbonized to create a unique interconnecting macroporous conducting carbon membrane. The conducting membrane is employed as a substrate for growing MoSe2nanosheets vertically using a simple solvothermal process. The electrochemical performance of the self-standing MoSe2-based heterogeneous binder-free materials was successively evaluated for HER.The excellent electrochemical hydrogen generation exhibited a low onset potential of −0.15 Vvsthe reversible hydrogen electrode and a Tafel slope of 51 mV/decade. In addition, remarkable stability with no current decay for over 20,000 s of testing was observed. The perpendicularly oriented nanostructure of the electrocatalyst on a highly carbon-porous electrode favored more exposedactive sites. Such, an open 3D structure leads to an easily diffused electrolyte in which the exposed active edges of MoSe2nanostructures are a key issue to fully realizing the excellent electrochemical properties.

N,S-co-doped FeCo Nanoparticles Supported on Porous Carbon Nanofibers as Efficient and Durable Oxygen Reduction Catalysts.

Finding high-performance, low-cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)-supported nitrogen (N) and sulfur (S) co-doped three-dimensional carbon nanofibers (FeCo-N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as-prepared FeCo-N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N2 and O2 -saturated. The experimental results revealed that FeCo-N,S@CNFs were highly active ORR catalysts with defect-rich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCo-N,S@CNFs exhibited a high onset potential (Eonset =0.89 V) and half-wave potential (E1/2 =0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as-prepared FeCo-N,S@CNFs catalysts was maintained for 14 h with long-term stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, Co-N@CNFs, Fe-N@CNFs, and varying Fe and Co ratios were compared with those of FeCo-N,S@CNFs. Synergistic interactions between metals and heteroatoms were believed to play a significant role in enhancing the ORR activity. Owing to their excellent catalytic reduction ability, the as-prepared FeCo-N,S@CNFs can be widely used in battery-based systems and replace commercial Pt/C in fuel cell applications.

Multi-configuration structure based on catalysis electrodes and composite membrane for efficient alkaline water splitting

The rational design of an efficient, stable, and safe alkaline water splitting system with non-precious metal catalysts is crucial for efficient sustainable energy conversion, but their practical application still remains a significant challenge. Here we show two highly efficient catalytic electrodes, cobalt-doped nickel/iron layered double hydroxide (Co:NiFe-LDH) nanosheets and nickel/iron alloy (NiFe-Alloy) nanoparticles grown on nickel foam, for the oxygen and hydrogen evolution reactions. What’s more, a novel composite membrane through a self-cross-linked reaction between Co:NiFe-LDH nanospheres and polyvinyl alcohol (PVA) has been prepared, constructing a dual dynamic framework structure for transporting ions and water molecules. The as-prepared composite anion exchange membrane (Co:NiFe-LDH@PVA) exhibits high stretchability and mechanical strength, strong hydrophilicity, and good ionic conductivity. As a result, the alkaline water-splitting electrolyzer affords a low cell voltage of 1.419 V at 10 mA cm−2 as well as robust stability over 100 h. Our study provides a new avenue for rational design and modulation of alkaline water splitting and holds great promise for developing renewable energy.

Construction of Ni‐Co‐Fe Hydr(oxy)oxide@Ni‐Co Layered Double Hydroxide Yolk‐Shelled Microrods for Enhanced Oxygen Evolution

AbstractThe exploration of earth‐abundant and efficient electrocatalysts toward the oxygen evolution reaction (OER) is critical for sustainable energy storage and conversion devices. In this work, we report a self‐engaged strategy to fabricate a yolk‐shelled OER electrocatalyst. Starting with a metal–organic framework, Co‐Fe layered double hydroxide (LDH)@zeolitic imidazolate framework‐67 (ZIF‐67) yolk‐shelled structures are formed in one step. Afterwards, these ZIF‐67 building blocks are transformed into Ni‐Co LDH nanocages to form the Ni‐Co‐Fe hydr(oxy)oxide@Ni‐Co LDH yolk‐shelled microrods (NiCoFe‐HO@NiCo‐LDH YSMRs) through an ion‐exchange reaction. Owing to the structural and compositional merits, the NiCoFe‐HO@NiCo‐LDH YSMR electrocatalyst exhibits an overpotential of 278 mV to reach the current density of 10 mA cm−2, a small Tafel slope of 49.7 mV dec−1, and good stability in alkaline media.

Construction of Ni‐Co‐Fe Hydr(oxy)oxide@Ni‐Co Layered Double Hydroxide Yolk‐Shelled Microrods for Enhanced Oxygen Evolution

The exploration of earth-abundant and efficient electrocatalysts toward the oxygen evolution reaction (OER) is critical for sustainable energy storage and conversion devices. In this work, we report a self-engaged strategy to fabricate a yolk-shelled OER electrocatalyst. Starting with a metal-organic framework, Co-Fe layered double hydroxide (LDH)@zeolitic imidazolate framework-67 (ZIF-67) yolk-shelled structures are formed in one step. Afterwards, these ZIF-67 building blocks are transformed into Ni-Co LDH nanocages to form the Ni-Co-Fe hydr(oxy)oxide@Ni-Co LDH yolk-shelled microrods (NiCoFe-HO@NiCo-LDH YSMRs) through an ion-exchange reaction. Owing to the structural and compositional merits, the NiCoFe-HO@NiCo-LDH YSMR electrocatalyst exhibits an overpotential of 278 mV to reach the current density of 10 mA cm-2 , a small Tafel slope of 49.7 mV dec-1 , and good stability in alkaline media.

Magnetic Field-Assisted Construction and Enhancement of Electrocatalysts.

Driven by the energy crisis and environmental pollution, developing sustainable clean energy is an effective strategy to realize carbon neutrality. Electrocatalytic reactions are crucial to sustainable energy conversion and storage technologies, and advanced electrocatalysts are required to improve the sluggish electrocatalytic reactions. The magnetic field, as a thermodynamic parameter independent of temperature and pressure, is vital in the construction of electrocatalysts and enhancement of electrocatalysis. In this Review, the recent progress of magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis is comprehensively summarized. Originating from the structure-activity-performance relationship of electrocatalysts, the fundamentals of the magnetic field-induced construction of electrocatalysts, including the magnetocaloric effect, nucleation and growth, and phase regulation, have been illustrated. In addition, the magnetic effect on the electrocatalytic reaction, namely, the magnetothermal, magnetohydrodynamic and micro magnetohydrodynamic, Maxwell stress, Kelvin force, and spin selection effects, are discussed. Finally, the perspective and challenges for magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis are proposed.

Hierarchical Cu2O/NiFeCo layered double hydroxide nanoarrays on copper foam obtained by a self-sacrificial templated route for a highly efficient oxygen evolution reaction

The design of highly active, economical and highly stable electrocatalysts for the oxygen evolution reaction (OER) is very important for realizing sustainable energy conversion. Herein, a Cu2O/NiFeCo layered double hydroxide electrode on a copper foam (CF) with a nanoarray structure (Cu2O/NiFeCo LDH/CF) is fabricated by using Cu(OH)2 on CF (Cu(OH)2/CF) as a self-sacrificial template. The prepared Cu2O/NiFeCo LDH/CF has a unique hierarchical nanostructure, high electrochemical active area and excellent integration of Cu2O and NiFeCo LDH, resulting in low overpotentials of 228 mV and 269 mV for current densities of 10 and 100 mA cm−2 in 1 M KOH, respectively, as well as an ultrasmall Tafel slope of 40 mV dec−1. In highly alkaline 6 M KOH, a overpotential of only 213 mV can deliver a current density of 100 mA cm−2. Moreover, the assembled water hydrolysis device operates stably for 50 h without a significant change in the potential in the strong alkaline solution. This high-efficiency OER performance and long-term stability make Cu2O/NiFeCo LDH/CF promising for practical applications.

In-situ constructed Cu/CuNC interfaces for low-overpotential reduction of CO2 to ethanol.

Electrochemical CO2 reduction (ECR) to high-value multi-carbon (C2+) products is critical to sustainable energy conversion, yet the high energy barrier of C-C coupling causes catalysts to suffer high overpotential and low selectivity toward specific liquid C2+ products. Here, the electronically asymmetric Cu-Cu/Cu-N-C (Cu/CuNC) interface site is found, by theoretical calculations, to enhance the adsorption of *CO intermediates and decrease the reaction barrier of C-C coupling in ECR, enabling efficient C-C coupling at low overpotential. The catalyst consisting of high-density Cu/CuNC interface sites (noted as ER-Cu/CuNC) is then accordingly designed and constructed in situ on the high-loading Cu-N-C single atomic catalysts. Systematical experiments corroborate the theoretical prediction that the ER-Cu/CuNC boosts electrocatalytic CO2-to-ethanol conversion with a Faradaic efficiency toward C2+ of 60.3% (FEethanol of 55%) at a low overpotential of -0.35V. These findings provide new insights and an attractive approach to creating electronically asymmetric dual sites for efficient conversion of CO2 to C2+ products.

Heterostructure Engineering of 2D Superlattice Materials for Electrocatalysis.

Exploring low-cost and high-efficient electrocatalyst is an exigent task in developing novel sustainable energy conversion systems, such as fuel cells and electrocatalytic fuel generations. 2D materials, specifically 2D superlattice materials focused here, featured highly accessible active areas, high density of active sites, and high compatibility with property-complementary materials to form heterostructures with desired synergetic effects, have demonstrated to be promising electrocatalysts for boosting the performance of sustainable energy conversion and storage devices. Nevertheless, the reaction kinetics, and in particular, the functional mechanisms of the 2D superlattice-based catalysts yet remain ambiguous. In this review, based on the recent progress of 2D superlattice materials in electrocatalysis applications, the rational design and fabrication of 2D superlattices are first summarized and the application of 2D superlattices in electrocatalysis is then specifically discussed. Finally, perspectives on the current challenges and the strategies for the future design of 2D superlattice materials are outlined. This review attempts to establish an intrinsic correlation between the 2D superlattice heterostructures and the catalytic properties, so as to provide some insights into developing high-performance electrocatalysts for next-generation sustainable energy conversion and storage.

(Digital Presentation) Design of Metal/Metal Oxide Nanomaterials for Highly Active, Selective, and Durable Electrocatalysts

Electrocatalysis is a key part of renewable energy conversion in the future energy system. Sustainable energy conversion and chemical production require catalyst structure with high activity, durability, and product selectivity. In general, nanoscale electrocatalysts suffer various degradation phenomena during electrocatalysis, which leads to critical performance loss. Recently, the various hybrid nanostructures (such as ordered structure, metal/carbon encapsulation, or metal/metal oxide) have been highly investigated to achieve promising catalytic performances and enhanced stabilities.In this presentation, we will cover three different types of nanomaterials as highly active and stable electrocatalysts for oxygen reduction reaction (ORR). First, the alloy nanoparticles with ordered structures exhibit novel catalytic properties from their unique electronic and geometric structures. In particular, Pt alloys with atomically ordered crystal structures have been found to largely improve both electrocatalytic activity and stability for ORR through increased electronic interaction between Pt and other transition metals. Similarly, we recently demonstrated that well-controlled Co-, Mn- and Fe-based ternary or binary oxide nanocatalysts have an exceptionally high ORR activity, in addition to the promising electrocatalytic stability. Therefore, it is very important to synthesize well-ordered alloy nanocrystals to obtain highly durable and active electrocatalysts with respect to their structural and compositional properties. Second, we will show the strategic employment of carbon shells on electrocatalyst surfaces to enhance stability in the electrochemical process. Carbon shells can beneficially shield catalyst surfaces from electrochemical degradation and physical agglomeration. Thus carbon shells can effectively preserve the initial active site structure during electrocatalysis. The carbon shell also provides a confined environment at interfaces, enabling unconventional electrochemical behaviors. Finally, we will suggest an effective strategy to construct metal/oxide interfaces, precisely modulating the metal/oxide interfacial interactions in the nanoscale. By controlling the interface and strain effect on catalytic activity, we can achieve high active and stable metal oxide systems for ORR. We would like to describe the details of the above results, for investigating structure-activity relationships in electrocatalytic processes. Only when we start to comprehend the fundamentals behind electrocatalysis on the structure and interface of metal/metal oxide nanocrystals, they can be further advanced to be sustainable in long-term device operation.

Machine Learning and High Throughput Synthesis Acceleration of the Discovery of Alkaline Electrolyte Oxygen Evolution Reaction Electrocatalysts

Accelerating the development and discovery of new catalysts is vital for advancing many electrochemical energy conversion technologies (EECT) required to achieve a sustainable future utilizing carbon-free fuel, a circular economy, and to meet the grand energy challenges of the 21st century. The oxygen evolution reaction (OER) is at the heart of many EECT such as water and carbon dioxide electrolyzers, fuel cells, and metal-oxygen batteries. The sluggish kinetics of oxygen electrocatalysis, resulting high overpotential necessary to attain practical current densities, and the high cost of the state-of-the-art OER platinum group metal (PGM) and precious metals catalysts (i.e., IrO2 and RuO2) limit the cost-effective implementation and development of several promising electrolysis technologies.1-3 The development of alternative PGM-free OER catalysts, with comparable or superior activity and durability to the PGM catalysts and derived from earth-abundant materials has thus been an active research area for decades.The application of perovskite oxides as PGM-free electrocatalysts for the OER in alkaline environments has seen significant research interest in the last decade, with tri-metallic and tetra-metallic compounds showing activities comparable to PGM-based catalysts.4,5 The chemical space of these compounds is exceptionally large, yet the development of new perovskite oxides with high OER performance (activity and durability) has been limited and often discovered through trial and error, a time and cost inefficient route that restricted the discovery of more advanced materials. Recent advances in high-performance computing, machine learning (ML), and high throughput material synthesis and screening technologies have enabled high-throughput catalyst design and discovery.4-10 This presentation will describe how the machine learning and high throughput synthesis technologies worked synergistically to accelerate the discovery of alkaline oxygen evolution reaction electrocatalysts. The role of ML in accelerating the materials synthesis and the role of high throughput synthesis in optimizing the ML model predictions will be discussed.AcknowledgmentsThis work was supported by the U.S. Department of Energy, Advanced Research Projects Agency-Energy (ARPA-E) under the DIFFERENTIATE program. This work was authored in part by Argonne National Laboratory, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.References Katsounaros, Ioannis, Serhiy Cherevko, Aleksandar R. 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Stoerzinger, Sokseiha Muy et al. "Tuning perovskite oxides by strain: electronic structure, properties, and functions in (electro) catalysis and ferroelectricity." Materials Today31 (2019): 100-118.Gómez-Bombarelli, Rafael, Jennifer N. Wei, David Duvenaud, José Miguel Hernández-Lobato, Benjamín Sánchez-Lengeling, Dennis Sheberla, Jorge Aguilera-Iparraguirre, Timothy D. Hirzel, Ryan P. Adams, and Alán Aspuru-Guzik. "Automatic chemical design using a data-driven continuous representation of molecules." ACS central science4, no. 2 (2018): 268-276.

Enhanced photoelectrochemical water oxidation on BiVO4 by addition of ZnCo-MOFs as effective hole transfer co-catalyst

Solar-driven water splitting is one of greenways for massive conversion of sustainable and nonpolluting energy applied to meet global energy crisis. Photocatalysts are greatly explored to improve photoelectrochemical (PEC) water oxidation efficiency. Bismuth vanadate (BiVO4) has been extensively used as photocatalyst for water oxidation, but its passive oxygen evolution kinetics and charge carrier recombination lead to inferior PEC performance under light illumination. Tuning interfacial charge separation and transfer is an eminent way to stimulate water oxidation characteristics of BiVO4. Herein, a BiVO4/zinc cobalt metal-organic framework (ZnCoMOF) composite is firstly proposed as photocatalyst for water oxidation. ZnCoMOF nanosheets are loaded on BiVO4 surface as co-catalyst via solvothermal process. Effects of solvothermal duration and mole ratio of zinc and cobalt are investigated. The optimal BiVO4/ZnCoMOF electrode shows a photocurrent density of 3.08 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), which is 4.21 times greater than that of BiVO4 electrode. The redox properties of high valence metal ions in ZnCoMOF are used to store photoexcited holes and transfer them to the water oxidation process in the BiVO4/ZnCoMOF system. This work demonstrates that PEC performance of BiVO4 can be largely improved via controlling water oxidation kinetics and refining charge recombination and transport properties.

Flower-like Co3O4@NiFe-LDH nanosheets enable high-performance bifunctionality towards both electrocatalytic HER and OER in alkaline solution

Exploring highly active and cost-effective metal-based overall water splitting catalysts are crucial for the large-scale conversion of sustainable electrical energy to fuels, feedstocks and green economy. Here, a nickel foam-supported electrocatalyst consisting of a one-dimensional Co3O4 nanowire and two-dimensional NiFe-LDH nanosheets is reported. The optimized Co3O4@NiFe-LDH/NF catalyst affords 79 and 215 mV at 10 mA cm−2 for catalyzing the hydrogen and oxygen evolution reaction in 1.0 M KOH, which also exhibits quick reaction kinetics and excellent durability. The self-supported electrode only requires 1.58 V to afford 10 mA cm−2 with astonishing stability for water splitting. The linked interfacial nanostructure between NiFe-LDH and Co3O4, which supports the enhancement of the electronic structure and increases catalytic active sites, is primarily responsible for the electrode’s remarkable catalysis performance. The Co3O4@NiFe-LDH/NF as an ideal electrocatalyst lays forth a broad technique for synthesizing electrocatalytic materials for efficient and scalable water splitting.

Recent Advances in Upgrading of Low‐Cost Oxidants to Value‐Added Products by Electrocatalytic Reduction Reaction

AbstractRecently, the efficient upgrading of abundant and cheap substances (H2O, CO2, N2, and NOxn) into valuable products by reduction and/or hydrogenation has attracted much attention. However, the traditional transformation processes of these oxidants generally suffer high‐energy input, complicated reactors, and rigorous reaction conditions due to their high thermodynamic stability and kinetic inertness. Recently, electrocatalytic reduction reactions (ERRs) for upgrading low‐grade substances have been perceived as promising for sustainable energy conversion due to the ambient condition, high selectivity, and atom economic feasibility. In this review, value‐added fuels and chemicals generation from low‐cost oxidants ERRs are systematically summarized. Specifically, H2 generation from ERR is introduced from water and seawater electrolysis; carbon‐containing compound generation from electrocatalytic COx reduction is classified into C1, and C2 and/or C2+ acquisition; valuable NH3 production is divided into nitrogen reduction reaction (NRR) and NOxn species reduction reaction (NOxnRR); and other valuable chemicals generation from multi‐substance reduction to CC bonds and CN bonds are also reviewed. This review aims to provide a comprehensive overview of high‐valued product generation from ERRs. Besides, an in‐depth understanding of such ERRs to valuable products has been presented, and current challenges and further prospects are also proposed.

Binder-Free Fabrication of Prussian Blue Analogues Based Electrocatalyst for Enhanced Electrocatalytic Water Oxidation.

Developing a cost-effective, efficient, and stable oxygen evolution reaction (OER) catalyst is of great importance for sustainable energy conversion and storage. In this study, we report a facile one-step fabrication of cationic surfactant-assisted Prussian blue analogues (PBAs) Mx[Fe(CN)5CH3C6H4NH2]∙yC19H34NBr abbreviated as SF[Fe-Tol-M] (where SF = N-tridecyl-3-methylpyridinium bromide and M = Mn, Co and Ni) as efficient heterogeneous OER electrocatalysts. The electrocatalysts have been characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS). In the presence of cationic surfactant (SF), PBAs-based electrodes showed enhanced redox current, high surface area and robust stability compared to the recently reported PBAs. SF[Fe-Tol-Co] hybrid catalyst shows superior electrochemical OER activity with a much lower over-potential (610 mV) to attain the current density of 10 mA cm−2 with the Tafel slope value of 103 mV·dec−1 than that for SF[Fe-Tol-Ni] and SF[Fe-Tol-Mn]. Moreover, the electrochemical impedance spectroscopy (EIS) unveiled that SF[Fe-Tol-Co] exhibits smaller charge transfer resistance, which results in a faster kinetics towards OER. Furthermore, SF[Fe-Tol-Co] offered excellent stability for continues oxygen production over extended reaction time. This work provides a surface assisted facile electrode fabrication approach for developing binder-free OER electrocatalysts for efficient water oxidation.

Design of a Metal/Oxide/Carbon Interface for Highly Active and Selective Electrocatalysis.

Sustainable energy-conversion and chemical-production require catalysts with high activity, durability, and product-selectivity. Metal/oxide hybrid structure has been intensively investigated to achieve promising catalytic performance, especially in neutral or alkaline electrocatalysis where water dissociation is promoted near the oxide surface for (de)protonation of intermediates. Although catalytic promise of the hybrid structure is demonstrated, it is still challenging to precisely modulate metal/oxide interfacial interactions on the nanoscale. Herein, we report an effective strategy to construct rich metal/oxide nano-interfaces on conductive carbon supports in a surfactant-free and self-terminated way. When compared to the physically mixed Pd/CeO2 system, a much higher degree of interface formation was identified with largely improved hydrogen oxidation reaction (HOR) kinetics. The benefits of the rich metal-CeO2 interface were further generalized to Pd alloys for optimized adsorption energy, where the Pd3Ni/CeO2/C catalyst shows superior performance with HOR selectivity against CO poisoning and shows long-term stability. We believe this work highlights the importance of controlling the interfacial junctions of the electrocatalyst in simultaneously achieving enhanced activity, selectivity, and stability.

Unraveling the Role of Defects in Electrocatalysts for Water Splitting: Recent Advances and Perspectives

The development of highly efficient and robust electrocatalysts plays a crucial role in the success of sustainable energy conversion technologies, like electrochemical water splitting for hydrogen production. Defect engineering has been considered as an effective strategy to tune the electrocatalysts and enhance the activity. This review covers recent advances in engineering, probing, and understanding the defects in electrocatalysts toward the hydrogen evolution reaction and oxygen evolution reaction. In particular, the role of defects in electrocatalysts have been comprehensively discussed and summarized on the basis of both experimental results and theoretical calculations. We further provide a summary of the computational insight into the role of defects. Finally, we propose the critical challenges and corresponding future directions.

Amorphous chromium oxide confined Ni/NiO nanoparticles-assembled nanosheets for highly efficient and stable overall urea splitting

Applications of urea oxidation reaction (UOR) in various sustainable energy-conversion systems are greatly hindered by its slow kinetics. Herein, we demonstrate an in-situ confined synthesis method that produces amorphous chromium oxide confined Ni/NiO nanoparticles-assembled nanosheets (Ni/NiO@CrOx) with fast reaction kinetics towards UOR. The confinement effect of the in-situ generated CrOx overlay contributes to ultrafine Ni/NiO nanoparticles, bringing about rich Ni/NiO and NiO/CrOx interfaces. In-situ Raman and electrochemical characterization show that both CrOx and metallic Ni can promote the formation of the NiOOH species and the electron transfer, leading to high intrinsic activity and fast reaction kinetics. At 1.40 V vs. reversible hydrogen electrode, the Ni/NiO@CrOx delivers a current density of 275 mA cm−2, which is about 2.6 and 6.1 times as large as those of the NiO@CrOx and NiO, respectively. In addition, the protective effect of the CrOx overlay leads to robust working stability towards UOR. Further, the Ni/NiO@CrOx nanosheets are used as bifunctional catalysts for overall urea splitting, and a small electrolysis cell voltage of 1.44 V is needed to reach the benchmark current density of 10 mA cm−2.

Atomic doping modulates the electronic structure of porous cobalt phosphide nanosheets as efficient hydrogen generation electrocatalysts in wide pH range

Developing efficient electrocatalysts to achieve sustainable hydrogen production from electrocatalytic water splitting remains a task of great significance and challenges. Atomic doping is of importance to enhance the performance of electrocatalysts by modulating the local microenvironmental of the designed nanomaterials. Herein, we have developed a porous CoP electrocatalyst with Ru and B atoms co-doping (Ru/B-CoP). Benefiting from the atomic doping and the unique multivacancy nanosheet structure, only 39 mV, 52 mV, and 87 mV are required to achieve 10 mA cm−2 for HER in 0.5 M H2SO4, 1 M KOH, and 1 M PBS, respectively, and also achieves excellent performance in seawater. It is shown that the introduction of Ru, B in CoP can successfully regulate the electronic structure of the samples and can provide enormous potential in the field of sustainable energy storage and conversion.

Hydrothermal carbonization of food waste as sustainable energy conversion path

Every day, a large amount of food waste (FW) is released into the environment, causing financial loss and unpredictable consequences in the world, highlighting the urgency of finding a suitable approach to treating FW. As moisture content makes up 75% of the FW, hydrothermal carbonization (HTC) is a beneficial process for the treatment of FW since it does not require extensive drying. Moreover, the process is considered favorable for carbon sequestration to mitigate climate change in comparison with other processes because the majority of the carbon in FW is integrated into hydrochar. In this work, the reaction mechanism and factors affecting the HTC of FW are scrutinized. Moreover, the physicochemical properties of products after the HTC of FW are critically presented. In general, HTC of FW is considered a promising approach aiming to attain simultaneously-two core benefits on economy and energy in the sustainable development strategy.